

Parked my car as usual in a open public car park for work but when I got back to her I immediately spotted this 15in curved crack on my windscreen

At first, I was fuming and I suspected it must have been some tw-at who had thrown a stone at the windscreen, but when I got home the above type of windscreen damage just doesn't add up cos, usually, the type of windscreen damage vandals cause would often be a 'bulls eye' or 'star break' type of impact damage.
I'm really baffled by this and I'm trying to understand why this windscreen damage has appeared. Could it be a manufacturing defect? There was certainly no stone chip before this crack appeared when I was driving. If there was, then it must have been a very minor chip without me noticing it.
Thought I'd open this up for opinions, or any similar experiences because I'm getting paranoid about whether to park there again.

Getting the windscreen replaced this Saturday so I can't get an professional opinion on the cause until then.